Asthma admissions and thunderstorms: a study of pollen, fungal spores, rainfall, and ozone

Asthma admissions have been reported to increase during thunderstorms. In s ome cases, this has been attributed to rises in pollen or fungal spore coun ts occurring alone or in combination with rainfall. We tested the hypothesi s that thunderstorms in general are associated with asthma admissions, and investigated the possible roles of pollen, fungal spores, ozone, and other meteorological factors. We obtained data on multiple pollen and fungal spor e counts, rainfall, temperature, ambient ozone concentrations, and asthma a dmissions for 32 dates when lightning strikes were recorded in the Cardiff/ Newport area, and 64 matched dates in previous and subsequent years. Poisso n regression models were used to investigate associations between admission s and proposed causative environmental factors. The number of asthma admiss ions was greater on days with thunderstorms than on control days (p < 0.001 ). There were no associations or interactions between admissions and any po llen or fungal spore counts or rainfall. After adjusting for thunderstorms, there was an independent association between increasing ozone concentratio n, when temperature was included in the model, and increasing admissions (p = 0.02). Asthma admissions are increased during thunderstorms. The effect is more marked in warmer weather, and is not explained by increases in gras s pollen, total pollen or fungal spore counts, nor by an interaction betwee n these and rainfall. There was an independent, positive association betwee n ozone concentrations and asthma admissions.